1. Field of the Invention
The present invention relates to an electrolytic regeneration unit for electrolyzing and regenerating a treatment liquid used in desmearing in the process of manufacturing printed wiring boards and the like, and also to an electrolytic regeneration apparatus using the electrolytic regeneration unit.
2. Background Art
When through holes or via holes are formed with a drill or a laser in resin substrates for use in printed wiring boards, smear, which is resin debris, is generated by the heat caused by friction between the drill or laser and the resin. In order to maintain electric connection reliability in the printed wiring boards, it is necessary to perform a treatment (desmearing treatment) of removing the smear generated in the through holes or via holes by using a chemical treatment method or the like.
A solution of a permanganate such as sodium permanganate and potassium permanganate is typically used as a treatment liquid in the aforementioned chemical treatment method. The treatment liquid is stored in a desmearing tank. Where the resin substrate is immersed in the treatment liquid in the desmearing tank and desmearing is performed, the smear is oxidized and removed from the through holes or via holes. In this process, the permanganate in the treatment liquid is converted into a manganate. Accordingly, in order to reuse the treatment liquid after the treatment for desmearing, an electrolytic regeneration treatment is performed for converting the manganate contained in the treatment liquid into the permanganate.
The conventional electrolytic regeneration apparatus is provided with an electrolytic regeneration tank in which the treatment liquid is stored, electrodes immersed in the treatment liquid in the electrolytic regeneration tank, a feed pipe that feeds the treatment liquid discharged from the desmearing tank into the electrolytic regeneration tank, and a return pipe that feeds the treatment liquid after the electrolytic regeneration to the desmearing tank. The treatment liquid circulates between the desmearing tank and the electrolytic regeneration tank. In such an electrolytic regeneration apparatus, a plurality of electrodes is usually provided inside the electrolytic regeneration tank to improve the regeneration efficiency (see, for example, Japanese Patent Publication No. 3301341).
However, in a system in which a plurality of electrodes are provided inside the electrolytic regeneration tank as described hereinabove, it is necessary to increase the capacity of the electrolytic regeneration tank (the capacity is about 1 time to 2 times that of the desmearing tank), the installation surface area for installing the electrolytic regeneration tank should be ensured, and the bath amount (liquid amount) increases.